The present invention relates to a device for recovering anaesthetic during the use of inhaled anaesthetics. The device is connected to a patient and comprises an anaesthetic evaporator for supplying anaesthetic to the patient and an absorption filter for absorption and desorption of the medium.
In the evaporator a fresh gas flow is conducted past the anaesthetic, in liquid phase, whereupon the medium evaporates in part of the fresh gas flow. This gas is mixed incompletely or unevenly with the gas breathed by the patient when it enters the tube since it enters through said opening. Since the supply of anaesthetic is also affected both by the flow and pressure of the gas breathed by the patient, it is difficult to know how much anaesthetic is actually being supplied to the patient.
The absorption filter is in the form of a body or container holding active carbon, for instance, in granular or powder form. Large quantities of such material are necessary for the absorption effect to be efficient. This means that the filter must be large and thus requires considerable space as well as increasing the quantity of carbon dioxide that is re-inhaled. The material must also be surrounded by a suitable filter to prevent the granules/powder from flowing into the patient""s lungs. The carbon also absorbs a certain amount of gas which therefore fails to benefit the patient. In some cases the breathing resistance may be considerable.
When using the device according to SE-B 459 155 it is impossible to abruptly alter or disconnected the supply of anaesthetic to the patient since some medium remains in the absorption filter. The remaining medium is admittedly gradually aired out but this takes time and in the meanwhile the patient is receiving an undesired supply of anaesthetic.
Neither does the device according to SE-B 459 155 allow the supply of anaesthetic to be closed off should the patient temporarily stop breathing.
One object of the present invention is at least partially to eliminate the summary of the invention provide a device having one or more of the following advantages:
Supply of anaesthetic to the gas breathed by the patient in exact quantities and in such a manner that the consumption of anaesthetic can be accurately controlled.
The absorption filter requires little volume and takes up little space, in spite of breathing resistance being maintained or decreased.
The absorption filter need not be surrounded by an extra filter.
The supply of anaesthetic from the absorption filter to the patient can be quickly cut off.
The supply of anaesthetic from the evaporator to the patient can be closed off if the patient stops breathing temporarily.
This object is fulfilled by the device according to the invention being given the features defined in the characterizing part of the claims.